Conceptual Design for a Vehicle with Rigid Lift Tanks 



This design is similar to the preceeding two, except for the ballasting 

 system. Two ring-stiffened cylinders constructed of HY-130 or HY-150 

 steel, sealed and filled with air, provide the required 20-ton lift capacity. 

 Design details are included in Appendix C. An expendable 20-ton concrete 

 ballast weight must be carried by the vehicle until the load is secured. The 

 ballast weight is then dropped (the load now serves as ballast) and the lift 

 vehicle proceeds to the construction site. Upon arrival at the site, the vehicle 

 pilot carefully positions the load, partially floods the lift tanks such that the 

 submerged weight of the vehicle minus the load is near neutral, detaches the 

 load, and proceeds to the surface. 



The vehicle operator must be especially careful that he does not dump 

 the ballast weight or detach the load prior to readjusting the vehicle buoyancy 

 to a near neutral state. Failure to do so will result in an abrupt, hazardous 

 ascent. After positioning the load at the new site, the operator must be 

 certain that he does not overflood the lift tanks, an oversight which could 

 result in the loss of the vehicle. In the latter emergency, the personnel 

 capsule could be jettisoned and its inherent positive buoyancy would insure 

 return to the surface. The problem of overflooding the ballast tanks could 

 be avoided if the vehicle carried sufficient fixed buoyant material to 

 compensate for the deadweight of the fully flooded tanks. This design would 

 also require an expendable ballast weight of approximately 40 tons — twice 

 the weight as before. It is assun"i3d, here, however, that ballast tank flooding 

 can be accurately monitored and controlled by the vehicle operators, thus 

 resort to the heavier and more costly "fail-safe" design is not necessary. 



Conclusions 



Table 1 1 compares features of all three competing, heavy-lift 

 submersibles.. Each of the three submersibles discussed has serious design, 

 developmental, and operational problems. Development of the high-pressure 

 helium vehicle places considerable strain on current and near future capabili- 

 ties in pressure vessel fabrication. The five 6-foot diameter tanks will be 

 vulnerable to damage during launch and retrieval or to accidental impacts 

 while transporting loads at the sea floor. With the development of higher 

 strength steels and titaniums, more compact and safer vehicles could be 

 designed. 



79 



